LONDON, June 28 (Reuters) - Two former editors of a British tabloid newspaper shut down by owner Rupert Murdoch over a phone-hacking scandal lost a legal battle on Friday to have criminal charges against them dropped.

Rebekah Brooks and Andy Coulson, both former News of the World editors and close associates of Prime Minister David Cameron, have pleaded not guilty to charges that they conspired to intercept people's voicemail messages in pursuit of stories.

Their lawyers had argued that once a message had been heard by its intended recipient it was no longer "in the course of transmission" as defined by the Regulation of Investigatory Powers Act under which the charges were brought.

The hacking scandal prompted Murdoch to shut down the mass-selling Sunday tabloid in July 2011 and led to a huge police investigation and to a public inquiry that revealed embarrassingly cosy ties between the media and politicians.

The judge in charge of the hacking case had rejected the defence arguments advanced by lawyers for Brooks, Coulson and three other former News of the World staff in May, but this could not be reported at the time for legal reasons.

The defendants appealed, but the Court of Appeal upheld the earlier judgment on Friday and allowed it to be reported.

"There is no good reason why the first receipt of the communication should be considered as bringing the transmission to an end," the Court of Appeal judges wrote.

The ruling means that Brooks, Coulson and others will stand trial as planned in September on hacking and other charges.

Brooks and Coulson both deny charges of involvement in the bribery of public officials for stories, and Brooks also denies perverting the course of justice.

Brooks, who after leaving the News of the World went on to edit its sister paper the Sun, Britain's highest-selling newspaper, later became the boss of Murdoch's entire British newspaper arm until the hacking scandal forced her out.

In her heyday, she enjoyed close friendships with senior politicians including Cameron.

After leaving the News of the World, Coulson went on to work as Cameron's chief of communications. He was forced out of that job in January 2011 as the hacking scandal gathered pace.